Aemulatio
by Row93
Summary: Sure, Batman's proteges work together like a well-oiled machine, Duke has seen this first-hand. But what Bruce forgot to tell him is that outside their uniforms, his new family members are one hundred percent pure unadulterated siblings. Or. Duke learns what it's like to be part of the ridiculousness that is the Wayne Family. (Btw HOW is Duke not a character on this site yet!)
1. Chapter 1

Hi, people who read this!

Just wanted to let peeps know that I keep my stories mostly on Archive of our own these days.

That's where I edit out my mistakes the most and where I usually update first.

This website is usally a bit of an afterthought for me.

I will keep putting my stories here as well however, because once upon a time it was the website that got me into the wonderful world of fanfiction.

But if you want timely updates etc, be sure to find me on AO3 under the same name!

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Duke Thomas prides himself on _knowing _lots of things. He knows how to take care of himself. He knows how to lead a group. He knows how to punch someone. These days he knows how to hack a computer. How to pick any lock. How to properly punch someone. In twenty different ways. There is one thing he doesn't know though, and that's what it's like to have siblings.

Because, sure, Batman's proteges work together like a well-oiled machine, Duke has seen this first-hand. But what Bruce forgot to tell him is that _outside _their uniforms, his new family members are one hundred percent pure unadulterated siblings.

1.

It starts off as a friendly sparring session. Duke is in the cave, working on a case for Tim who's sick in bed (the others shrugged when he mentioned that; Duke feels like there's more to it) papers scattered all around him. He's been trying his best to make sense of Tim's chicken scrawl to a background of steadily increasing insults. Jason and Damian have been at it on the sparring mats for the past half hour and at first they were just taunting each other in between well placed punches and kicks. By now their language is evolving so colourfully that Duke can't help but cringe every now and then. He's about to gather up all his casework and move to the study upstairs to work in peace when it happens.

The drop that makes the cup run over. The straw that breaks the camels back. Two emotional hot-heads who have just pushed each others buttons a bit too much.

"If you fight like this it's no wonder Father let you DIE!"

A silence falls over the cave. Duke turns around, his arms full of paper, just in time to see Jason's face go scarily blank. And _oh_ he knows that look.

"So you still think you're so much better than us, huh?", Jason snarls, wiping sweat from his face. He shakes out his bangs before raising his fists again, all quiet calm and determination, "Then prove it, ya fucking brat."

Damian, to his credit, holds out longer than Duke expects.

Jason lets Damian come to him, blocking several jabs and punches, letting a few connect to lure Damian into a false sense of victory. He waits till Damian has to flip back to catch his breath for a second before going on the offense, throwing out wild, savage punches and kicks, forcing Damian to resort to acrobatics to avoid him.

Duke knows that Damian is able to take down opponents that are bigger than him. He has to, because almost everyone _is_ bigger than him. But Jason is bigger and _stronger. _He's the tallest and the heaviest of all the Wayne kids; Duke is pretty sure he weighs more than Bruce even.

Damian jumps out of the way of another sweeping kick and lands in a crouch, breathing hard now. Duke watches him, sees him narrowing his eyes, setting his jaw. And then the kid is moving again, ducking under Jason's left hook, launching himself in the air to deliver a roundhouse kick to the face. And for a fraction of a second Duke believes that the kid is going to beat Jason. Then all of sudden Jason has Damian's outstretched leg in an iron grip and throws him to the floor with so much force Duke sucks in a breath. Damian's shoulder hits the mats, and he manages to turn his rough landing into a roll, but when he raises his head up Jason's fist is waiting for him.

_Crack._

The sound reverberates through the cave. Duke almost drops his papers, ready to break up the brothers if he has to. A second passes. Then Damian's hands fly to his face and a groan escapes from the kid's lips. Blood starts streaming from underneath his fingers, dripping from his chin onto his t-shirt.

Uh oh, Duke thinks.

"Fuck." Jason says and drops to his knees, trying to pull away his brother's hands to survey the damage, "Shit. I'm sorry!"

Damian is not having it, slapping Jason's hand away with his left while trying to pinch the bridge his nose with his right. It's not helping. Blood splatters on the mats, making the whole scene only look more dramatic.

"You broke my fucking nose!" Damian yells angrily and Duke sees Jason throw nervous looks at the stairs to the manor.

"Calm down, Dami," Jason tries to shush him, "I didn't even hit you that hard."

"You BROKE my nose!" Damian repeats, the redness in his face not just coming from the blood anymore, "I'll be benched for a week!"

"Shut up. Just sh.."

Duke is pretty sure that clamping a hand over your little assassin brother's mouth is a bad idea, but clearly Jason fears something else more than being bitten by a demon child. Duke realises this might be the right time to bail, before he gets dragged into it.

"What the _hell_ is going on here!"

As Duke turns around, Bruce is suddenly there on the stairs, looking pissed beyond measure. Duke watches as the man's cool blue eyes take in the sweaty mats, the blood on Damian's face and Jason's stricken expression.

"We were just sparring," Jason starts, a nervous quality in his voice that Duke doesn't hear often from him and Duke takes that as his que to make like a tree and leave, Tim's casework be dammed. He holds his arms up in surrender as he passes Bruce, muttering "I had nothing to do with this," and takes the last few steps two at the time. The last thing he hears, is Bruce growling about the 'no injuries while sparring' rule before he shuts the grandfather clock behind him. He takes a deep breath, rolling his shoulders then sets of in search of Tim. If what he just observed can be considered a normal sibling experience, he needs to know how to prepare.


	2. Chapter 2

2.

The second incident is more subtle and all the more confusing to Duke because of it. Tim has manned the couch in the den, after being deemed well enough to leave his bed, and now he and Duke are pouring over Tim's case together. They're trying to find a correlation between several robberies in the east end and a new phone store that popped up in the same neighbourhood. It seemed a bit far-fetched to Duke at first, but he knows that Tim has a nose for these kind of things.

So they have two laptops, a tablet, casefiles, police reports, print-outs of crime scene photos and numerous stationary articles spread out over the coffee table. Duke circles another sentence in a police report and shows it to Tim, who sticks his hands from under the blanket he has wrapped himself in and makes grabby motions. Duke hands the paper to him and gets to work on the next one. It's a rhythm they easily settle into. Duke doesn't talk much, just reports his observations to Tim every now and then. Tim doesn't talk at all, curtesy of a sore throat, and only uses different _hmms _to let Duke know what he thinks.

They look up in sync when the door to the den opens and Damian walks in. He's carrying a tray with two steaming mugs and wearing his favourite scowl on his face.

"Pennyworth told me to bring you _refreshments._" he says, making sure the last word is dripping with disdain. Duke shuffles their work around to create some free space for the tray and looks up just in time to spot the exchange of glares between Damian and Tim.

Duke asked Dick once why there seemed to be so much animosity between the two youngest Waynes. Dick told him that Damian was _troubled _when he first came to them. Duke has figured out since that _troubled_ in Bat-speak actually means murderous intent.

But Duke is also aware of the delicate truce between the brothers these days. Damian has ceased to be _troubled_. Tim doesn't seek out Damian's company like he does his other siblings, but also doesn't actively avoid him. The current exchange of glares is something else though. And Duke wonders if this is another sibling thing that he is missing.

Damian sets the tray down, turns around and leaves. Duke decides he wants nothing to do with whatever is going on between Damian and Tim and takes one of the coffee mugs. He pulls the sugar pot closer and prepares to add a royal amount to hi-

"_Don't._" Tim warns, and Duke almost startles at the sound of his rough, unused voice. He turns around to look at him, spoon still in his hand and Tim smirks. Duke has come to recognise it as his I'm-smart-and-I-know-it smirk.

"Taste it." Tim instructs, and Duke carefully dips a finger into the sugar then brings it to his mouth. He discovers quickly that he has nearly added a shit ton of _salt _to his coffee. Damian planned this, he thinks with a shock. When he looks at Tim, the realisation in his eyes, Tim snorts at him.

"Never trust helpful siblings.", Tim states, like it's a mantra he has repeated to himself more than once. Duke nods, still a bit confused, and files it away. Tim picks up another case file and starts reading it like nothing happened. Duke stares at him for a while, then picks up his marker to continue his work as well.

They drink their coffee black.


	3. Chapter 3

3.

The third thing that happens is not entirely unfamiliar to Duke, because he does actually have friends who like to goof around. But it still catches him by surprise to see it happen with his new family. In hindsight though, he should have seen it coming. The Robins are a competitive bunch after all.

Alfred cajoled them all into doing a 'family activity', so the boys bickered about which movie to go see until Bruce shut them all up and picked the new Blade Runner remake. It ends up being a good choice. Even Damian (who spluttered angrily when an employee needed Bruce's approval to let him into the R rated movie) seemed to enjoy it.

And now they're all patiently waiting in the lobby, ready to get pizza somewhere, while Bruce is _happily_ chatting with an acquaintance he has unfortunately stumbled upon.

"- _One thing is sure, the Wayne heirs are all blessed in the hair department_." Dick reads out the tweet from his phone. Duke and Tim snort, Damian just huffs. Jason tuned them all out about five seconds after they started playing this game, doing who-knows-what on his own phone.

"Hear that, Jay?" Dick says, flicking Jason's ear, "We're all blessed. Except for you. Because you know. You're _dead_." And he pulls on the white lock hanging over Jason's forehead. Jason swats his hand away.

"Fuck you, Dickhead, I'm proud of this. It's my badge of honour." Jason responds, running a hand through his hair, "I can't believe B tried to bully me into dying it."

Duke has heard bits and pieces about Jason's story. He knows Jason doesn't have an official civilian identity at the moment and that Bruce is careful about his public association with the 'Wayne Family'. Jason also never shuts up about his apparent _death._ Duke hasn't had the balls yet to ask the whole story. Something about stirring up a hornets nest.

"I can't believe B hasn't bullied Timmy into getting a haircut yet." Dick changes the subject, choosing to ruffle Tim's too long hair instead. Tim lets it happen but does let out a very Batman like grunt, "B can't tell me what to do. I'm an e-"

"- mancipated minor." Jason, Dick and Damian finish together, like they rehearsed it. Duke snorts again.

"I hate you all." Tim responds ruefully, but there's a smile pulling on the corner of his mouth.

"No, you don't." Dick states, picking up his phone again, "Alright, next one-"

"Father seems to be done." Damian cuts him off, and they all look up to see Bruce walking up to them, obvious relief on his face that his conversation is over and that he can drop his 'most eligible bachelor' persona.

That's when it happens.

There's a sudden eye-contact between the brothers. At first Duke thinks he's imagining it, but then he spots the matching grins growing on their faces. Behind him Bruce lets out a sigh-

"LAST ONE TO REACH THE PARKING LOT IS A DOUCHE CANOE!" Dick roars and Duke has no time to react before he's roughly shoved out of the way by Jason, who sets off in a sprint after Dick and Tim. Duke ends up right into Damian's path and the kid actually snarls at him as he pushes Duke away and takes off in pursuit of his older brothers.

Duke only needs a millisecond to recover his wits, sees Bruce shake his head dejectedly from the corner of his eye and decides, _fuck it, I can play this game too. _He lets out a war cry as he overtakes Damian and then bodily tackles Jason to the ground, who in turn takes down a screaming Tim with him.

And Duke feels like _maybe_ he's finally getting the hang of the whole sibling thing, even if it ends up being Dick who declares his victory over them all.


	4. Chapter 4

4.

By the time the fourth thing happens, Duke realises that his brothers have started to use these _incidents _as sibling education for him, and he's not sure how he feels about that. So far it's a weird mix between honoured and patronised.

In the meantime, Dick is also trying to educate Duke in the ways of _tactical brain training _as he calls it. Which is just his bullshit way of saying that he's getting his ass kicked in Overwatch.

They're on their third match when Tim comes shuffling into the den, dressed in sweats and with a blanket wrapped around his shoulders. Duke watches him slowly makes his way over to the armchair from the corner of his eye, all messy hair and red rimmed eyes.

Duke plucked up the courage to ask Tim about his seemingly crappy immune system last week and to his surprise the guy just lifted his shirt and pointed at a ragged scar along his stomach. "Turns out spleens do important shit for your body." he'd said. When Duke asked how it happened, Tim just pointed to Damian and said, "Ask his grandpa."

Once again the saying 'stirring up a hornet nest' came to mind. There seem to be a lot of hornet nests with this family Duke has discovered. But he's not stupid. He won't stir them up all at once.

Tim watches them play for a while, giving hints and joining Duke in his exasperation when Dick once again forgets who his team members and who his opponents are. After they lose another match Tim gets up, saying "I'm going back to bed," and starts shuffling his way out again. Dick watches Tim with narrowed eyes, then starts up another match.

"You see, Duke," Dick says, eyes not leaving the screen, "There are a few things you just need to know about this family."

"Enlighten me." Duke responds, mashing buttons, like that will help them win faster. This is where the education comes in. He wonders what wisdom Dick will bestow on him today.

"One." Dick starts, "Jason can't be trusted to make rational decisions concerning jobs. He'll always end up in trouble, or making trouble."

Duke snorts.

"Two." Dick continues, "Damian can't be trusted to make rational decisions concerning animals. One word: _Bat-cow _." He lets out a cry of triumph as he takes someone down.

"That's two words."

"It's hyphenated. And three. Tim can't be trusted to make rational decisions concerning his health."

Duke raises his eyebrows at him. Eyes still not leaving the screen Dick opens his mouth and yells, "Alfreeeed! Tim is trying to steal his laptop back!"

There's the immediate sound of a door opening and an exasperated "_Master_ _Tim!_"

Duke looks over his shoulder to see Tim standing awkwardly in the hallway, looking like a deer caught in headlights, laptop half hidden under his blanket. He shoots his older brother a look of utter betrayel.

"What about you?" Duke asks, turning back to Dick.

"Me?", Dick shrugs, "I can't be trusted to make rational decisions concerning my family's wellbeing."

And maybe, Duke thinks, that's a good thing.


	5. Chapter 5

5.

The fifth incident is when Duke realises he needs to stop counting these, because it will likely never stop anyway. Everytime he thinks he knows what he's doing, one of his brothers will appear and prove him that he knows nothing at all. And that's just the guys.

Because there's also Cass.

Cass is...a complete mystery to Duke. She shows up at the manor every now and then, to spend time with her brothers. But no one ever knows when she'll appear. She never announces her visits, and never seems to use the front door. Sometimes she stays for a few hours, sometimes a few days. Cass just _materialises_ and then vanishes again. When she arrives, everyone is happy to see her. Even Bruce smiles more whenever his daughter is around.

The problems start, Duke has found out, _after_ Cass has visited.

Because Cass likes to borrow things. And return them much later, or not at all. And Duke knows its Cass. They all know it. They just haven't been able to prove it. Yet.

Duke is quietly reading in the library, trying his best to ignore the sounds of bickering coming from the living room. Jason has misplaced his favourite red sweater and has been interrogating every single member of the family. When Bruce asked him if he hadn't just left it at one of his safe houses, Jason scoffed and said he wasn't a slob like _Dickface_. Now Dick, Bruce and Jason are having a discussion that Duke has been trying to tune out for the last twenty minutes. He doesn't notice he's succeeded until he looks up from his book and realises it's quiet again.

Duke tries to focus back on his book when he hears the tell tale squeak of a window opening behind him. When he turns around to look he's not the least bit surprised to see Cass sneaking in, wearing Jason's red sweater. Although on her it looks more like a dress.

"Hey, Cass." Duke greets her with a grin. The fact that she's used this particular squeaky window tells Duke that she wanted him to hear her.

"Hi, Duke," she smiles back at him, "Intel for Tim." She pulls a flash drive from the front pouch of Jason's sweater and waves it at him. "But I'm busy."

"Sure, I'll give it to him." Duke replies and takes the flash drive from her. He eyes the sweater, "Jason's been looking for that."

Cass grins then whispers, "Don't tell him. Will give it back soon."

Duke shrugs. He wasn't planning on getting involved anyway. He just wanted to give Cass a heads up. He likes Cass.

"Thanks, Duke."

She waves at him before disappearing through the window again. Duke picks up his book to continue reading. It only lasts a few minutes, until he's interrupted again. This time by Jason sticking his head around the corner.

"Yo, Duke, you happen to see my sweater anywhere? The red one?"

Duke considers telling the truth for exactly one second. Then he remembers that he has learned one thing about siblings in the past few weeks: there's a time for honesty and there's a time for causing chaos. This is obviously the latter.

"Nah man, I haven't seen it, sorry." Duke answers, knowing full well he can get away with it because the others still think he's settling in and getting used to them, "Maybe ask Tim? I think I saw him wearing something red today."

Jason's eyes narrow, "That little _shrimp_. Of course it's him. Always borrowing shit without asking -"

Duke watches Jason stalk off, muttering things under his breath, then he picks up his book once again with a smirk.

It may have taken him a few weeks, but he finally figured out how to get a handle on this whole sibling thing. It's easy really. You just need to know how to built up goodwill and when to use that goodwill for your own ends. And most importantly, just remember the rule: Cass _never_ does anything wrong.


	6. Chapter 6

+1

Duke didn't think that, of all things, a rotten wooden beam would be his demise. Then again, he also didn't think he'd ever be a vigilante, trying to gather intel on an illegal weapons ring by himself, in the middle of the night. But here he is, being backed into a corner by at least a dozen career criminals, his arm cradled to his chest to keep his dislocated shoulder from being jostled. It's funny how things can go.

He looks around, mind racing, trying to come up with some way, any way to get out of this alive, but he comes up empty. The only thing that might be of slight use right now are his flash grenades. But even those will never give him enough time to get clear of the building, with the state his arm is in. It's better than nothing though. So Duke slips one the one tiny metallic balls from his glove into his hand, just like Batman taught him.

His assailants don't see it coming, but they are well trained and only need a few moments to get their bearings back. As the room is lit up by blinding light Duke barely manages to scramble away, and all he can do is hide behind some stacked crates. It's stupid really. They all know where he is. He just prolonged the inevitable.

And maybe that tiny sliver of fear that settled in the pit of his stomach at the start of this night has developed into full blown fear. Because he's not ready to go yet. He was gonna do so much more good in the world as Signal.

He's so close to just giving up when all of a sudden the building goes dark. Duke sucks in a breath, and judges by the similar sounds coming from the the crooks in the room that they didn't plan this either. They start yelling to each other, panic clearly breaking out.

And amidst the fear in Duke's stomach a tiny bit of hope comes back in. _Are they actually coming for him? _

There's the unmistakable sound of a smoke pellet being smashed on the floor and then all hell breaks loose. Duke has no idea who is the room with him, but he can clearly hear that the criminals are on the losing side. He barely holds in a yelp when a red helmet pops into his view.

"Hey D, how are you doing?" Jason says, his voice slightly distorted by his helmet, "Thought we'd pop in for a bit, see how our newest member is doing."

Duke is pretty sure he is crying at the moment and he doesn't give a shit.

"W..we?" Is all he manages to get out.

"Oh, sure." Jason drawls, "We got the tiny Red hacking shit, Big Bird is having fun punching people, and Babybird was supposed to be on watch, but I'm pretty sure that's him over there knocking people out too."

Duke just nods, relieve flooding through him so fast it almost makes him giddy. Then he lets out a hiss when Jason touches his arm.

"You injured badly?"

Duke shakes his head, his jaw clenched, "Nah, just dislocated it."

While Jason checks out his shoulder the sounds of fighting around them die down, and not much later it's just Nightwing and Robin standing between a dozen unconscious goons lying on the floor. They give their handiwork a satisfied look. Then Red Robin drops in from the ceiling right between them and high fives first Nightwing, then a reluctant Robin. Duke lets himself being pulled up by Red Hood, and they stand awkwardly for a moment.

"Thanks, guys." He manages to bring out, "I uh… definitely thought I was a goner for a sec there."

He shuffles his feet a bit, then he's enveloped in a hug. Duke doesn't know what to do for a second. He hasn't been hugged before by any of his new family members. He thought they weren't there yet. But then he realises he doesn't care right now, because he just want to let himself be held by Dick. Wants to bask in the feeling of having people look out for him again.

"You're our brother, Duke." Dick says into his ear, "Of course we were coming for you." and he can't help the smile breaking out on his face at that.

After everyone has made sure that Duke indeed has nothing more than a dislocated shoulder, they spent some time tying up the criminals. Jason gives Duke the honor of alerting the cops. They watch the GCPD arrive from the next roof over, before scattering in the wind again. Only Tim stays behind and offers Duke to patch him up at his apartment.

"B doesn't need to know you got hurt." He tells Duke in a staged whisper and Duke gives him a surprised look, "How'd you know I was out there alone?"

Tim snorts.

"Please. Like _we _have never gone out by ourselves when we just started out. It's basically an initiation ritual." He smirks at Duke,"So I guess this is your official welcome. You're now to hold yourself forever to the siblings won't tell rule. Within reason that is."

Duke grins.

"I think I can do that."


End file.
